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Pre-convolved Radiance Caching, EGSR 2012


Pre-convolved Radiance Caching

Daniel Scherzer     Chuong H. Nguyen     Tobias Ritschel     Hans-Peter Seidel

MPI Informatik



Paper Abstract

The incident indirect light over a range of image pixels is often coherent. Two common approaches to exploit this inter-pixel coherence to improve rendering performance are Irradiance Caching and Radiance Caching. Both compute incident indirect light only for a small subset of pixels (the cache), and later interpolate between pixels. Irradiance Caching uses scalar values that can be interpolated efficiently, but cannot account for shading variations caused by normal and reflectance variation between cache items. Radiance Caching maintains directional information, .eg to allow highlights between cache items, but at the cost of storing and evaluating a Spherical Harmonics (SH) function per pixel. The arithmetic and bandwidth cost for this evaluation is linear in the number of coefficients and can be substantial. In this paper, we propose a method to replace it by an efficient per-cache item pre-filtering based on MIP maps --- such as previously done for environment maps --- leading to a single constant-time lookup per pixel. Additionally, per-cache item geometry statistics stored in distance-MIP maps are used to improve the quality of each pixel's lookup. Our approximate interactive global illumination approach is an order of magnitude faster than Radiance Caching with Phong BRDFs and can be combined with Monte Carlo-raytracing, Point-based Global Illumination or Instant Radiosity.

Materials for Download

The paper (Adobe Acrobat PDF, 3.2 MB).
The video (AVI, 20.2 MB).
The Slides (TBD).

Citation


Daniel Scherzer, Chuong H. Nguyen, Tobias Ritschel, Hans-Peter Seidel
Pre-convolved Radiance Caching
Computer Graphics Forum 31(4) (Proc. EGSR 2012), 2012.

  @article{scherzer:2012:PreconvolvedCaching,
   author  = {Daniel Scherzer and 
              Chuong H. Nguyen and
              Tobias Ritschel and              
              Hans-Peter Seidel},
   title   = {{Pre-convolved Radiance Caching}},
   journal = {Computer Graphics Forum (Proc. EGSR 2012)},
   volume  = 4,
   number  = 31,
   year    = {2012}
  }

Acknowledgements

We would like to thank Tania Pouli for the video voice-over.